The present invention relates to a frequency coupling position coordinates determination apparatus using an electromagnetic induction system, or to a daisy type or a data tablet.
In a conventional position coordinates determination apparatus of this type, a current flows through an electromagnetic coil provided to a pen or cursor, and a magnetic flux generated from the electromagnetic coil is detected by a plurality of one-turn coils arranged on a flat plate, thereby determining a position of the pen or cursor on the basis of a detection result.
FIG. 1 shows an example of such a conventional apparatus. A position coordinates determination apparatus shown in FIG. 1 has a circular coil 1 incorporated in a pen or cursor, and N (positive integer) one-turn coils 2-1, 2-2, . . . , 2-k, 2-(k+1), . . . , 2-(N-1) and 2-N arranged on a printed circuit board 3. The circular coil 1 freely moves on an area 4 of the printed circuit board 3 where coordinate reading is performed. In the example shown in FIG. 1, the circular coil 1 is placed on the one-turn coils 2-k and 2-(k+1). In this case, when a current flows through the circular coil 1, an induced current flows through the one-turn coils 2-k and 2-(k+1) and does not flow through the other one-turn coils. If it is determined whether the induced current flows through the respective one-turn coils or an amplitude of the flowed induced current is determined, a current X position coordinate of the circular coil 1 in the area 4 can be calculated. This conventional apparatus also includes detectors 5-1, 5-2, . . . , 5-k, 5-(k-1), . . . , 5-N for detecting the amplitude of the above induced current, and a calculator 6 for calculating the current X position coordinate of the circular coil 1 on the basis of the amplitude of the N induced currents detected by the above detectors. The same arrangement as described above is provided with respect to the Y coordinate, so that X and Y position coordinates of the circular coil 1 in the area 4 can be determined.
As described above, the conventional apparatus requires a large number of detectors each constituted by integrated circuits, resulting in a complex and large apparatus.